Signal unit for telephone



July 27, 1954 E. S. PETERSON SIGNAL UNIT FOR TELEPHONE CONVERSATION RECORDERS Original Filed Nov. 12, 1948 ATTORNEY um 2 Aw I; b m- 3;: m2: m; Mm m =5 M mm CE nu NH 5 m o 2 NH run ON u nun 7...?N HM... r j m; s 0 0 a D I l 528% m x u M In L E S 2- Jon I M mm r-T L. l J a 2 U a i f m m J N 3 3 8 .11 on F mm H mm ET U 2 T o 21 [l N rIL m: r 8 8 3 f mm v w a 5mm 2 F :2? 256 w h NI Reissued July 27, 1954 UNITED STATES SIGNAL UNIT FOR TELEPHONE CONVERSATION RECORDERS Edward S. Peterson, Elmwood Park, 111., assignmto Automatic Electric Laboratories, 1110., Chicago, 111., a corporation of Delaware Original No. 2,530,075, dated November 14, 1950,

Serial No. 59,667, November 12, 1948. Application for reissue November 8, 1951, Serial No.

16 Claims.

reissue specification; matter printed in italics ind This invention relates in general to machines for recording telephone conversations, and is more particularly concerned with auxiliary apparatus for such a machine for giving a warning signal to the parties involved that the conversation recorder is in operation and that the conver sation is being recorded.

Arrangements for accomplishing this basic result are known, as by the obvious method for example, of adding a cam to the turntable, or to invention to provide a self-contained combination 1- signal-unit-and-connecting-box for a conversation recorder, which is suitable for use with any recorder, and which also provides that the tone unit must be in operation whenever the recorder is in operation to record a call.

It is another object of the invention to provide an intermittent audible signal which will be both distinctive and unmistakable, without great volume or intensity, and without detriment to either the conversation or the recording.

Another object of the invention is the provision of simple means for separately varying the intensity of the signal as supplied to the line, to the near telephone, and to the recorder.

A feature of the invention is the manner of interconnecting the signal unit, the telephone, the line and the recorder so as to provide the proper volumes of speech and signals to each.

Another feature of the invention lies in the provision of two transformers in said signal unit connected in tandem with the signal generator at one end, the recorder at the other end, and the telephone and line connected between the trans formers, with means for shunting the recorder side of said connection while the signal is on to reduce the volume thereof to the telephone and recorder.

Another feature of the invention is the use of an electronic oscillator and amplifier and an elec tronic timer in the signal unit, and a relay controlled by said timer for applying the signal and connecting up the volume reducing means.

Other objects and features of the invention will be apparent from the specification and claims which follow, when considered in conjunction Matter enclosed in heavy brackets I: 1 appears in the original patent but forms no part of this hates additions made by reissue.

2 with the appended drawing, comprising the Fit,- ures 1 and 2, which illustrate one embodiment of the invention.

Figure 1 of the drawing illustrates in conventional circuit diagram form, the connecting and signal unit of the invention, and a portion of the associated equipment.

Figure 2 shows in idealized diagrammatic form, the general overall wave shape, or envelope, of the audible signal.

With further reference to the drawing, the signal unit proper includes everything in Figure 1 on the upper and right sides of the broken line 35, while on the under side of this line are shown an associated telephone line It, a telephone Hi, a recorder 28, and an alternative auxiliary starting device 2?. It will be noted that the telephone ill is connected to the line is through the tone unit, over a direct current loop circuit comprising the conductor It, winding 68 of the transformer 64, conductor E2, the telephone it, and conductors H and it. This loop is of course normally open at the hook-switch contacts, not shown, of the tele phone iii. The telephone Ill, which may be any conventional form of instrument, is also con nected in shunt across the condenser :33 and the winding 55 of the transformer (it, over the conductors l2, H and Hi.

The recorder 2B, which may be any conventional form of voice recording device, i here assumed to be a sound recording and reproducing machine generally similar to that shown and described in U. S. Patent 2,366,458, issued to Barton A. Proctor on January 2, 1945. A pair of contacts 2i added to this machine subsequently, are arranged to be operated by the control lever 22 only when it is moved to the recording position, so that it points to the letter R. The contacts 2i are unoperated when the lever 22 is in the normal, illustrated position, or when it is moved to the playback or listening position where it points to the letter L. A power switch, indicated by the small rectangle 23, is arranged to connect commercial power to the recorder and to the tone unit, by way of the plug ended cord 24 and the cord 26, which may also be a single cord of the Y connected type.

In case however, that the machine employed has no facilities for passing power in this manner to the signal unit, the cord 26 may also be a plug ended cord whereby the signal unit may be separately connected directly to the stated commercial power source. Furthermore, if no contacts ii are available in the recorder, a separate starting arrangement, consisting of a start-stoppush-button-set 21, shown in dotted lines, may be employed. Operation of the start button will connect conductors 50 and 3| in the same mannor as the contacts 2|, and a subsequent operation of the stop button will release the start button, and open its contacts, not shown.

The connecting signal unit, which may be conveniently mounted in a small housing no larger in size than a telephone ringer box, consists essentially of an electronic timer Bil controlling a signal relay ill, an electronic oscillatorand-amplifier Bil, a pair of tone transformers 54 and d, a power relay 55, and a single phase disc rectifier and associated filter, together with various resistors and capacitors as shown. This unit is connected to the telephone and line through the four line terminals shown at the left, and to the recorder by way of a seven prong plug receptacle 3'! shown at the lower right.

The timer 0, which employs an unbalanced multivibrator circuit, includes a dual triode vaouum tube 89, a pair of grid condensers 83 and ill of equal value, a pair or" unbalanced grid resistors 82 and 85 with the former having a much higher resistance than the latter, and a pair of unbalanced plate resistors 84 and G8 with the latter having the higher resistance. The left section of the tube thus has a long time constant in its grid circuit and the right section a short time constant, with the values so chosen that the left section is cut off or non-conducting for seconds, and conducts for second, while the right section is non-conducting for /5 second and conducts for 15 seconds. The signal relay H5 connected in the plate circuit of the left hand section is thus operated. for a period of approximately /5 second every 15 seconds. A. high value resistor 86 bridges around the grid condenser 8'? aids in causing the timing relay to release more quickly, by helping to drain the charge from the condenser 81 while the left section of the tube is conducting.

In the oscillator-amplifier 98, the oscillator, which employs the left section of a second dual triode tube IEH, is a simple Hartle oscillator of the stabilized grid and plate type, tuned to oscillate at a frequency of 1400 cycles per second. Its elements include, in addition to the tube, a blocking condenser 95 and an associated resistor 85, a grid condenser 54 and an associated grid leak resistor 93, and an oscillating or tank circuit comprising a two-section inductor S2 and an associated bridging condenser 5!. The amplifier, which raises the oscillator output to the proper level for application to the telephone line is a simple resistance-coupled one-stage unit comprising the right section of the tube HM, the coupling resistors 9? and 98, the grid condenser 99 and the grid resistor [M].

The amplifier output is connected momentari- 1y to the primary of the tone transformer 64 through the series condenser 61, each time the signal relay 78 operates. The secondary of this transformer is connected to the telephone line in series with the condenser 63 and the primary of the recorder coupling transformer 60, while the telephone H! is connected in parallel with a portion of this circuit as previously indicated. The secondary of the transformer 60 is connected to the speech input circuit of the recorder through make contacts 57 of the power relay 55, whenever this relay is operated, by way of a bleeded circuit 44 comprising the resistors 45 and 46. Where a recorder having automatic volume control is used, the recorder input will be connected across the entire resistance, by means of the strap or jumper 48, but Where the recorder used does not provide for automatic volume control, its input will be connected across the upper resistor only, by means of the strap 41, to avoid overloading the recorder. It will be herein assumed that the strap 48 is connected and the strap 41 omitted.

A very low value resistor T l is also arranged to be shunted across the bleeder resistors b the contacts 13 whenever the signal relay l9 operates to put the warning tone on the line. This greatly reduces the value of the splash of tone applied to the recorder. This is considered necessary to avoid mutilation of the record, since the volume of tone required for transmission to the distant end of the line would cause an excessive response in the recorder. It is desirable that the signal appear in the record, but only in reduced volume.

The power supply to the filaments of the tubes is 115 volts alternating current fed through a toggle switch 49, which is closed, together with the recorder switch 23, whenever it is desired to place the recorder in standby condition. The

filaments are in series with each other and with a variable resistor 59, which may be adjusted as necessary to maintain the filament current at the proper value. The plate supply is fed from the same 115 volt source through the switch 40 and a single phase disc rectifier unit M in series with a filter 42 comprising a filter choke and two filter condensers. Plate voltage is applied to the tubes however only when the power relay is operated to close contacts 55. The power relay 55 must also be operated to remove a direct short circuit, represented by the contacts 58, from across the recorderinput leads 32 and 33.

It is thus seen, that regardless of the particular type of recorder control employed, the recorder, when connected to the line through this unit, will not under normal conditions, record any conversations on the line, unless the tone unit is also in operation. This is obvious, since the power relay 55, which starts the oscillator and timer, must be operated to remove the shunt from the input circuit of the recorder, and to connect up the secondary of the transformer 63.

To place the recorder and signal unit in service, the telephone and line are connected to the signal unit line terminals as shown, and assuming the illustrated recorder 29 to be used, the multi-conductor plug, not separately shown, which terminates the recorder leads 3d and 35 inclusive, is plugged into the receptacle 3! and locked. The cord 24 is then plugged into the volt supply source. Since the recorder 20 is also assumed to have automatic volume control, the strap 48 on the voltage divider 44, which is normally connected, will be left in place.

To place the recorder in standby condition, ready for operation to record a call, it is now only necessary to close the recorder power switch 23 and the signal unit power switch 49. Filament current is thereby caused to fiow through the switch lit, the resistor 59 and the filaments of the tubes 89 and H3! in series, and the filaments heat up. Rectified power is also applied to one side of the power relay 55, through the rectifier 4!.

To start recording a conversation taking place over the line I3, it is now only necessary to move the recorder arm 22 to the recording position. The recorder contacts 2| are thereby closed, and complete a circuit to the power relay 55, over a circuit starting at one side of the power supply,

and passing over conductor 35, terminal i, switch 40, rectifier ll, filter 42, resistor 43, winding of relay 55, terminal 2, conductor 3!, contacts 2!, conductor 36, terminals l and E, and conductor 34 back to the other side of the power supply.

The power relay 55 thereupon operates, from the positive half cycles of current passed by the rectifier 4|, and remains operated during the recording. Relay 55 upon operating, at its contacts 58 removes the direct short from the leads 32 and 33 leading to the recorder input circuit, at its contacts 51 prepares another shunting circuit controlled from contacts 13-, and at its contacts 5% connects anode voltage to the oscillator and timer. Plate voltage now extends to the oscillator anode through the resistors 98 and 91, to the left anode of the timer through the resistor 3 and the relay 10, and to the right anode of the timer through the resistor 88.

The oscillator now starts to oscillate, at a frequency of 1400 cycles per second, and the timer starts to pulse rhythmically, over these circuits, with the two sides of the timer conducting in turn, in the manner previously stated. As each section of the timer conducts, it charges the condenser in its own grid circuit and draws the charge from the condenser in the opposing grid circuit until the triggering point is reached, when the other section begins to conduct and reverses the process in known manner. Each time the left section conducts, the timer relay T is operated for approximately- /5 second, as previously stated, over the circuit comprising the positive terminal of the rectifier M, the contacts 56,. the resistor 84, the relay iii, and the left anode and cathode of the tube 89 to the negative side of the same circuit, represented by ground.

Each time the relay H! operates in this manner, its contacts 12 open the normal shunt circuit around the condenser 61, contacts 13 connect the low resistance M across the recorder coupling circuit, between the transformer 85) and the bleeder resistors '35 and id, and the contacts H close the amplifier output circuit, which now extends from ground at the right cathode of the tube lill, through the tube to the right anode, contacts H, condenser ET, the primary winding 55 of tone transformer E4, and contacts 56 to the positive terminal of the rectifier 4|.

A splash of amplified 1400 cycle tone from the oscillator is thereby impressed on the primary of the transformer 64, and thence to the line l3, by way of the secondary winding 66, condenser 63!, the primary winding iii of the recorder coupling transformer 66 and the conductors Hi, i5 and i4.

Since this circuit is quite resonant at voice frequencies it puts the tone on the line at a relatively high value. The tone is at full volume only very briefly however, due to the attenuating action of the condenser 6'5, which as it .charges cuts the current flow down very rapidly. This gives the tone wave a shape generally like that shown in Figure 2, and provides a very distinctive audible signal, quite similar to the ping of a stringed instrument when one of the springs is plucked sharply. This assures that the signal will register through the conversation, even when considerably muted, or reduced in volume. It also assures a very short signal, as the tone is completely attenuated before the timer relay restores.

From the primary winding of the coupling transformer 60 the tone signal is further induced into the secondary winding 62, appears across the resistors 45 and 46 and passes therefrom to the recorder input circuit. Due to the fact that the low value resistor M is now bridged across the resistors and 46 by way of contacts is and the conductor 50, the volume of the tone signal actually impressed upon the recorder terminals, is very much reduced, so that when the recording is played back, the signal while still audible clue to its form, will not be too prominent. The shunting of the secondary of the coupling transformer E0 by the resistor 14 also causes a portion of the tone signal to be echoed or reflected back into the primary circuit, and thence to the telephone it which is connected in multiple with this circuit, as previously mentioned. The tone to the telephone H) is thus also considerably reduced in volume.

When the signal relay HI restores, at the end of the second conducting interval, its contacts 13 remove the shunt from the recorder coupling circuit, its contacts 11 open the amplifier output circuit leading to the tone transformer St, and its contacts 12 place a shunt around the tone attenuating condenser til. The condenser 81 thereupon discharges quickly through the shunting resistor 68, which has a comparatively low resistance, and is completely discharged long before the next operation of relay lil, some 15 seconds later.

At the end or the conversation, or whenever the recorder control lever 22 is restored to the neutral position, or is shifted to the play-back or listening position, the contacts 2i open the circuit to the power relay which restores. Relay 55 thereupon, at contacts 5'! disconnects the secondary of the recorder coupling transformer 60, and at contacts 58 replaces the direct shunt across the recorder input conductors 32 and 33. Relay 55 also, at its contacts 56 disconnects plate voltage from the oscillator and timer, which thereupon cease operation.

While there has been described what is at present considered as the preferred embodiment of this invention, it should be understood that various changes and re-arrangements may be made therein Without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. In a signal system, a telephone, a telephone line, a conversation recorder, a signal unit, said telephone, said line, said unit and said recorder being interconnected only electrically, a tone generator and a timer in said signal unit, manually operated means for conditioning said recorder to record a conversation occurring between said telephone and said line, a relay in said signal unit operated responsive only to the operation of said conditioning means, contacts on said relay, a normally short-circuited speech input circuit for said recorder, means including said contacts responsive to the operation or" relay for re-enabling said input circuit and for starting said tone generator and said timer, and means responsive to the operation of said generator and timer for transmitting an intermit tent audible signal simultaneously to said telephone, to said line, and to said recorder.

2. In a signal system as in claim 1, an output circuit for said tone generator, and a capacitor in said output circuit for passing the full volume of said signal only very briefly, and then quickly attenuating said signal.

3. A signal system as in claim 2, in which said output circuit includes a tone amplifier, and in which said capacitor is charged by the passage 7 of the signal after its amplification by said amplifier.

4. In a signal system, a telephone line, a conversation recorder, a signal unit having a signal tone generator and a timer therein, means for conditioning said recorder to record a conversation on said line, a start relay in said signal unit responsive only to the operation of said conditioning means for operating said tone generator and said timer, a first transformer in said unit for coupling said generator to said line, a second transformer in said unit for coupling said generator and said line to said recorder, a signal relay in said unit intermittently operated in response to the operation of said timer, contacts operated by said signal relay, means responsive to the operation of certain of said signal relay contacts for extending the signal tone output of said generator intermittently and simultaneously to said line through said first transformer and to said recorder through said first and second transformers, and other means responsive to the operation of others of said signal relay contacts for reducing the volume of the signal tone extended to said recorder only.

5. A signal system as in claim 4, wherein said signal reducing means comprises a resistor connected momentarily across the recorder side of said second transformer.

6. In a signal system comprising a line, a telephone, a voice recorder, and a signal unit all interconnected electrically only, a signal tone generator and a timer associated with said slgnal unit, means for conditioning said recorder to record speech originating in said telephone and said line, means responsive only to the operation of said conditioning means for operating said generator and said timer, a first transformer for coupling said generator to said line, a second transformer for coupling said generator and said line and telephone to said recorder, a signal relay having contacts operated at regular intervals responsive to the operation of said timer, circuit means responsive to the operation of certain of said relay contacts for extending the signal tone output of said generator intermittently through said transformers to said line, said telephone and said recorder simultaneously, and other circuit means responsive to the operation of others of said relay contacts for reducing the volume of the signal tone passed to said telephone and said recorder only.

7. A signal system as in claim 6 in which said telephone and line are interconnected by a direct current loop circuit including a winding on said first transformer, and in which said line is also acoustically connected to windings 011 both of said transformers in series, with said telephone connected acoustically in shunt across one of said windings.

8. A signal system as in claim 6, in which said line is connected in series with windings of both said transformers, in which said telephone is connected across one Winding of said second transformer and said recorder across the other winding, and in which said volume reducing means is also connected momentarily across said other winding of said second transformer while said tone signal is being extended.

9. The combination of a line, a recorder for recording messages passing over said line, a signal unit for impressing spaced audible warning signals on said line only when said recorder is actually recording messages passing over said line, an electronic tone oscillator for generating said signals, an electronic amplifier for raising the volume of said signals, an electronic timer for applying said spaced and amplified signals to said line during the time said recording is taking place, and capacitor means for attenuating said signals quickly following their application to said line to give said signals a characteristic sharp note.

10. In combination, a subscribers telephone line, a subscriber telephone set comprising a transmitter and a receiver connected to said line, a voice recorder, electronic me ns opereative to generate an intermittent tone of desired frequencg, and means compris ng two inductance coils coupling said line, telephone set, recorder and tone source, windings of both said coils being connected in series with said line and telephone set, another winding of one of said coils being connected to said electronic means, and another winding of the other of said coils being connected to said voice recorder, whereby voice currents re transmitted from said line and subset through one of said coils to said voice recorder and said intermittent tone is transmitted through the other inductance coil to said line and through both of said inductance coils to said recorder.

11. In a coupling and tone generating unit, a transformer for coupling a subscribers telephone line to a voice recorder at the subscriber station, a generator for generating an interrupted tone, and a transformer for coupling said generator to said line, windings of both of said transformers being connected in series with said telephone line and station, another winding of one of said transformers being connected to said generator, and another winding of the other of said transformers being connected to said recorder, whereby a warning tone current is transmitted from sa d generator over the telephone line and to the recorder.

12. In combination, a line, a telephone substation connected thereto, voice recording means, means including manually operable switching means for opcratively connecting said recorder to said line and telephone station, and means rendered operative by the connection of said recording means to said line to impress upon said line currents having variations of audible frequency as an indication that recording is taking place, and means for varying the amplitude of said currents on said line during the time they are applied.

13. In a coupling and tone generating unit for coupling a subscribers telephone line to a voice recorder at the subscriber station, a generator for generating a warning tone, an inductance coil having a winding connected in series with said line and another winding coupling said generator to said line, can inductance coil having a winding connected in series with said line and another winding coupling said line to said recorder, and means comprising an impedance network: tuned to said tone interconnecting said other winding of the last-mentioned inductance coil with said recorder, said network being efiective to reduce the level of the tone transmitted to said recorder.

14. In a recorder connector for connecting a conversation recorder in a telephone line, line connecting means for connecting said recorder connector in a telephone line including an audio transformer, terminals to provide connection between the transformer and the wires of a telephone line, means connected in circuit with said transformer to sound a tone warning at predetermined time intervals for a predetermined time duration, a terminal element, means connecting said terminal element with said tone warning sounding circuit means, voice current conducting means including means for connecting the voice current conducting means in circuit with said transformer, means for connecting said voice circuit conducting means with said terminal element, said terminal element including means for connection with a conversation recorder to transmit both the tone warning and voice to the recorder.

15. A. recorder connector as claimed in claim 14 wherein said tone warning sounding means and voice current conducting means and said term nal element are connected in electrical communication so that when one of the circuits is closed all must be closed and when one circuit is open the others are automatically opened whereby it will be impossible to transmit the voices to a recorder without transmitting the tone warning therewith.

References Cited in the file of this patent or the original patent UNITED STATES PATENTS Number Name Date 1,551,319 Meyberg Aug. 25, 1925 1,780,919 Holland Nov. 11, 1930 1,845,034 Bickelhaupt Feb. 16, 1932 2,340,159 Thompson Jan. 25, 1944 

